This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. "The goal of this study is to determine whether imaging of the brain every six months can predict the onset and monitor the progression of Alzheimer's disease. There is no treatment involved in this study. The imaging methods used will be Magnetic Resonance Imaging (MRI) and, for a subset of participants, Positron Emission Tomography (PET) scans. In addition to neuroimaging, the study will test blood, and, for some participants, cerebrospinal fluid (from lumbar puncture) to determine if biomarkers can predict and monitor the disease. There are approximately 50 participating sites across the country, with a total enrollment goal of 800. We will enroll three groups of participants: patients with mild to moderate Alzheimer's disease (AD), patients with Mild Cognitive Impairment (MCI), and normal controls. AD patients will be followed for a total of 2 years, MCI patients and controls for a total of 3 years. After an initial screening visit, participants will come to the clinic every 6 months to undergo imaging, physical exam, blood work, memory testing, and for some participants, lumbar puncture. There will also be surveys and questionnaires for a caregiver or study partner to complete. "